Flame retardant compositions

ABSTRACT

The resistance to both flaming and glowing combustion exhibited by polymer compositions wherein the flame retarding agent is comprised at least in part of a halogen-containing organic compound in combination with an antimony oxide is significantly increased by including specified halogenated phosphates, thiophosphates or thiophosphoryl chlorides as part of the flame retarding agent. The presence of sulfur in the composition reduces the total amount of flame retarding agent required to achieve an SE-0 rating in the UL 94 vertical position burning test.

BACKGROUND OF THE INVENTION

This is a division of application Ser. No. 361,895, filed May 21, 1973now U.S. Pat. No. 3,912,792.

This application is a continuation-in-part of application Ser. No.278,016, filed Aug. 4, 1972, now abandoned which in turn is acontinuation-in-part of application Ser. No. 175,694, filed Aug. 27,1971 and now abandoned.

This invention relates to improved flame retardant materials.

This invention further relates to a method for enhancing the flameretardancy imparted to inherently flammable materials by the combinationof antimony oxide with halogen-containing organic compounds.

The inherent flammability of many materials, including synthetic organicpolymers, has restricted their use for numerous applications,particularly in children's wearing apparel, in the constructionindustry, and as decorating materials for commercial aircraft andlocations of public accommodation. A variety of substances have beenused to impart flame retardancy to inherently flammable substrates.Halogen-containing organic compounds, particularly when used incombination with antimony trioxide, are effective flame retardingagents.

In the absence of a flame retardant, many materials are completelyconsumed by flame once they are ignited. The addition to many organicpolymers of about 37% by weight of a mixture comprising two to threeparts of a halogen-containing hydrocarbon and one part of antimonytrioxide yields a material which, at most, burns very slowly once theigniting flame is removed; however, at flame temperatures many of thesethermoplastic polymers melt to form liquids which burn and can,therefore, ignite flammable material with which they come in contact.This is most undesirable since it could result in spreading of a fire toareas which could otherwise be unaffected. In addition, once the flameis extinguished, the materials continue to glow for as long as severalminutes. The glowing areas generate vapors which could be toxic, andpresent the potential hazard of reigniting into flaming combustion underthe proper conditions. Increasing the concentration of flame retardantdoes little, if anything, to reduce the flaming and glowing types ofcombustion and more importantly, adversely affects the strength andother desirable properties of the substrate. The presence of manyadditives, including flame retardants, degrades the properties of theunmodified polymer to an extent which is usually proportional to theconcentration of the additive. This effect is particularly evident usingcrystalline polymers such as polypropylene and limits the amount ofadditives, including flame retardants, that can be present in acommercially useful product, which, in turn, limits the degree of flameretardancy that can be imparted using a given flame retarding agent.This has understandably resulted in a search for more efficient flameretarding agents which impart the highest possible degree of flameretardancy to a substrate at any given level of concentration.

One objective of this invention is to provide flame retarding agentswhich exhibit improved performance when compared with prior art productsat equivalent levels of concentration. A second objective of thisinvention is to provide a method for improving the performance,particularly the efficiency, of a known class of flame retardants.

It is well known to employ organic esters of phosphoric acid and otherphosphorous-containing acids to impart flame retardancy to variouspolymeric substrates. Up until now it has not been considered feasibleto employ these esters in combination with conventional flame retardantscontaining a halogenated organic compound and antimony trioxide since ithas been reported by Dr. C. P. Fenimore ("The Oxygen Index Test, AMeasure of the Flammability of Plastics", presented at the University ofDetroit Polymer Conference Series, June 8-12, 1970) that phosphorousdestroys the antimony-halogen synergism by preventing the volatilizationof antimony compounds. This conclusion is supported by experimental datain the accompanying examples. Surprisingly it has now been found thathalogenated aromatic phosphates, thiophosphates and thiophosphorylchlorides are unique among esters of phosphorous and thiophosphorousacids in their ability to enhance rather than inhibit the flameretardancy imparted to organic polymers by mixtures of antimony trioxidewith halogen-containing organic compounds.

The presence of sulfur in the flame retarding agent decreases the amountof flame retardant required to attain a given level of performance. Thisis considered surprising since sulfur has not been shown to impart anysignificant degree of flame retardancy to flammable organic polymers.

SUMMARY OF THE INVENTION

This invention provides an improved composition for imparting flameretardancy to organic polymers, said composition being comprised atleast in part of one or more halogen-containing organic compoundsexhibiting a volatilization temperature above 200° C. and selected fromthe group consisting of halogenated paraffinic, olefinic and aromatichydrocarbons, aliphatic hydroxylated compounds, aliphatic,cycloaliphatic and aromatic ethers, carboxylic acids and derivativesthereof, aldehydes, and ketones in combination with between about 8 and100% based on the weight of said halogen-containing organic compound, ofan antimony oxide, wherein the improvement resides in the presence of aphosphorus compound selected from the group consisting oftris(halophenyl) phosphates, tris(halophenyl) thiophosphates, andbis(halophenyl) thiophosphoryl chlorides wherein each phenyl groupexhibits at least three halogen atoms, in an amount between 0.5 and 20%,based on the combined weight of the halogen-containing organic compoundand antimony oxide, all of the halogen in said composition beingselected from chlorine and bromine. Optionally, the composition may alsoinclude up to 50% of sulfur, based on the weight of the phosphoruscompound.

This invention also provides a method for reducing the degree of flamingand glowing combustion and eliminating the dripping of molten materialexhibited by polymer compositions wherein the flame retarding agent iscomprised at least in part of one or more of the aforementionedhalogen-containing organic compounds and between 8 and 100%, based onthe weight of the halogen-containing organic compounds, of an antimonyoxide, the method comprising incorporating into the flame retardingagent between 0.5% and 20%, based on the combined weight of antimonyoxide and halogen-containing organic compound of one of theaforementioned phosphorus compounds and, optionally, up to 50% ofsulfur, based on the weight of phosphorus compound.

DETAILED DESCRIPTION OF THE INVENTION

The addition of one or more tris(halophenyl) phosphates, thiophosphatesor bis(halophenyl) thiophosphoryl chlorides to a polymer which has beenflame retarded using a mixture of an antimony oxide and at least onehalogenated organic compound significantly reduces the time required forboth the flame and glowing to be extinguished once the polymer isignited. The weight of phosphorus compound should not exceed about 20%based on the combined weight of the antimony oxide and halogenatedcompound. Above this level, the flame retardancy imparted to thesubstrate actually decreases rather than increases. This is believed dueto the adverse effect of phosphorus compounds on the synergistic actionof antimony oxide with the halogen-containing organic compound.

For example, the combination of 50 parts of perchloropentacyclodecane, apreferred halogen-containing compound and 17 parts by weight of antimonytrioxide, per 100 parts of polypropylene yields a composition whichburns for between 7 and 15 seconds following removal of the ignitingflame and exhibits an afterglow for between 40 and 120 seconds.Increasing the concentration of either halogen compound or oxide yieldsat best a slight decrease in burning and afterglow times and, moreimportantly, adversely affects the physical and rheological propertiesof the polymer to a significant extent. By contrast, the addition offive parts of a tris(tribromophenyl) phosphate to the aforementionedcomposition yields a substantial reduction in burn and glow timeswithout significantly affecting the physical properties of the polymer.The addition of halogenated alkyl phosphates have virtually no favorableeffect on flame retardancy.

The efficiency of the flame-retarding agents of this invention issignificantly increased by replacing up to 25% by weight of thephosphate with sulfur.

The flame-retarding agents of this invention are useful with manyclasses of natural and synthetic materials, including organic polymerswhich can be rendered flame retardant using the combination of anantimony oxide with a halogen-containing organic compound. Among thenatural organic polymers are cellulosic materials such as cotton, wool,and wood. The flame retarding agents of this invention exhibit efficacyin reducing both burning and glowing combustion of most syntheticorganic polymers including polyolefins, e.g. polyethylene andpolypropylene; vinyl polymers including polystyrene and polyvinylchloride; acrylic polymers including poly (methylacrylate) and polymerscontaining acrylonitrile, e.g. terpolymers of acrylonitrile, butadiene,and styrene; polyamides including nylon type polymers and polyestersderived from saturated and unsaturated acids, for example, fatty acids,and drying oils. The polyesters can be either linear or are crosslinkedusing appropriate curing agents, e.g. styrene. Epoxide polymers, e.g.those derived from the diglycidyl ether of bisphenol A[2,2-bis(4,4'-hydroxyphenyl) propane] or aliphatic alcohols or polyols,are also suitable substrates.

The halogen-containing organic compounds of this invention containbetween 2 and 20 carbon atoms and preferably contain two or three fusedcarbocyclic ring structures, one or more of which may be of the bicyclictype as represented by the formula ##STR1## and contain a plurality ofchlorine or bromine atoms to the extent that halogen atoms may occupyall of the valences not satisfied by carbon-carbon bonds. Thehydrocarbon radicals may be alkyl, cycloalkyl, aralkyl, aryl or alkaryl.Alternatively, the radical may contain one or more carbon to carbondouble bonds. Various functional groups, e.g. hydroxyl, carboxy andcarboxylate radicals may also be present on the molecule. Suitablehalogen-containing compounds are represented by the generic formulsRX_(m) Y_(n) wherein X represents a bromine or a chlorine atom, each Yis individually selected from the group consisting of hydrogen atoms andradicals exhibiting the formula ##STR2## R and R' each represents analkyl, cycloalkyl, aryl, alkaryl or aralkyl hydrocarbon radicalcontaining between 2 and 20 carbon atoms. Alternatively, the compoundmay be present in polymerized form.

The following Table lists some representative compounds from the variousclasses of suitable halogenated compounds and the types of polymericsubstrates wherein the compounds have been employed.

    ______________________________________                                        CHLORINATED COMPOUNDS                                                         ______________________________________                                                          USE                                                         ______________________________________                                        Alkanes                                                                       Chloroethanes     Paint, polystyrene                                          Chloropropanes    Polyesters                                                  Chlorinated C.sub.10 -C.sub.30                                                                  Paints, wood, textiles,                                      paraffins         polyolefins                                                Chlorinated fish oil                                                                            Paint                                                       Chlorinated rubber                                                                              Rubber                                                      Chlorinated PVC   Vinyls, textiles                                            Chlorinated polyisobutylene                                                                     Polyurethane                                                Chlorinated polyolefins                                                                         Polyolefins                                                 Polyvinyl chloride                                                                              Textiles                                                    Benzene hexachloride-                                                                           Cellulose derivatives                                        C.sub.6 H.sub.6 Cl.sub.6                                                     Olefins                                                                       Chloroethylenes, vinyl                                                                          Textiles, polystyrene,                                       chloride          acrylics                                                   Chloropropene     Polystyrene, vinyls,                                                           acrylics                                                   Chlorobutene and butadiene                                                                      Rubber, vinyls                                              Chloroprene       Polyolefins                                                 Vinyl chloroacetate                                                                             Polyesters, acrylics                                        Allyl chloride    Epoxies                                                     Hexachlorocyclopentadiene and                                                                   Paints, polyesters, poly-                                    derivatives ("hex")                                                                             urethanes, epoxies, poly-                                                     styrene, acrylics                                          Chlorendic acid and                                                                             Polyesters, polyurethanes                                    derivatives       epoxies, vinyls                                            Alcohols, acids, aldehydes and other functional compounds                     Chloroalcohols (C.sub.2 -C.sub.12) and                                                          Vinyls, polyesters                                           polyols                                                                      Pentaerythritol chlorohydrin                                                                    Polyesters, polyurethane                                    Tetrachlorobutane-1,4-diol                                                                      Epoxies                                                     Alcohols, acids, aldehydes and other functional                               compounds (continued)                                                         Epichlorohydrin   Epoxies                                                     1,1,1-Trichloro-                                                               2,3 epoxypropane Polyesters, polyurethane                                    Chloroadipic acid Nylon, vinyls                                               Vinyl chloroacetate                                                                             Polyesters                                                  Dichlorosuccinic acid                                                                           Polyurethane                                                Chlorinated fatty acids                                                                         Polystyrene                                                 Chloral           Polyurethane, epoxies,                                                         polyaldehydes                                              Chloroalkyl acrylonitrile                                                                       Acrylics                                                    Chlorinated aryldiamines                                                                        Epoxies                                                     Aromatics                                                                     Alkoxychlorobenzenes                                                                            Vinyls                                                      Chlorinated hexamethylbenzene                                                                   Vinyls                                                      Chlorinated alkylaryl ethers                                                                    Polyesters                                                  Chlorophenols     Textiles, styrene, acrylics,                                                   wood phenolics, poly-                                                         phenylenes                                                 Pentachlorophenol Polyurethane epoxies                                         glycidyl ether                                                               Chlorostyrenes    Polyesters, polystyrene,                                                       polyolefins                                                Chlorothiophenol esters                                                                         Acrylics, vinyls                                            Chlorinated 1,4-bis-                                                                            Cellulosics, textiles                                        hydroxymethyl benzene                                                        Chlorophenyl isocyanate                                                                         Textiles                                                    Chlorobiphenyls and                                                                             Textiles, polyesters,                                        polyphenyls       polyurethane, polystyrene                                  Chlorinated 4,4'-bis-                                                          hydroxy-biphenyl Polyesters                                                  Chlorinated 3,3'-bis-                                                          isocyanato-biphenyl                                                                            Polyurethanes                                               Chlorinated naphthalenes                                                                        Textiles, polyesters                                        Chlorinated bisphenol A and                                                    glycidyl ethers  Polyesters, epoxies                                         Chlorinated diphenyl carbonate                                                                  Polycarbonates                                              Tetrachlorophthalic acid and                                                   derivatives      Textiles, polyesters                                        Chlorinated alkyd resins                                                                        Paints                                                       ##STR3##          Vinyls                                                     ______________________________________                                    

    ______________________________________                                        BROMINATED COMPOUNDS                                                          ______________________________________                                                           USE                                                        ______________________________________                                        Alkanes                                                                       Bromoethanes       Vinyl Polymers                                             Bromocycloalkanes  Polyolefins                                                Bromocycloalkanol, acrylic acid                                               ester              Acrylic Polymers                                           Brominated polybutadiene                                                                         Vinyl and styrene polymers                                 Olefins                                                                       Vinyl bromide      Polystyrene, acrylics                                      Tetrabromododecene Polyesters                                                 Hexabromobicycloheptene deriv-                                                atives             Acrylics                                                   Brominated cyclododecatriene                                                  Hexabromo cyclopentadiene                                                     Alcohols, acids, aldehydes and other functional groups                        2,3,3-Tribromoallyl alcohol                                                                      Polystyrene, vinyls                                        and esters (e.g., acrylate                                                    esters)                                                                       2,2,3,3-Tetrabromobutane-                                                                        Polystyrene                                                1,4-diol                                                                      Brominated pentaeythritol                                                                        Polyesters                                                 Brominated polyols Polyurethanes                                              2,3-Dibromopropyl phthalate                                                                      Paper                                                      Brominated tall oil                                                                              Polyurethanes                                              2,2-Bis(bromomethyl)-1,3-                                                                        Polyesters                                                 propanediol                                                                   2-Bromoethyl itaconate                                                                           Polystyrene, acrylics                                      Dibromosuccinic acid                                                                             Polyesters                                                 Bromoacetaldehyde, bromo-                                                     benzaldehyde       Polyvinyl alcohol                                          Brominated amides -BrCH.sub.2 -R-                                             CONR.sup.1 R.sup.2, where RC.sub.3C.sub.2 ;                                                      Polyurethanes                                              R.sup.1, R.sup.2 are lower alkyls                                             Bis (2,3-dibromopropyl)                                                                          Polystyrene                                                malate                                                                        Aromatics                                                                     Brominated polyphenyls                                                                           Polyolefins                                                Pentabromotulene   Polyurethanes                                              Bromophenyl vinyl ether                                                                          Polyesters                                                 Styrene dibromide  Polystyrene                                                Bromophenols, acrylate esters                                                                    Paints, polystyrene                                        Bromophenol, glycidyl ether                                                                      Polyesters                                                  ##STR4##          Polyesters                                                 Bromotoluene di-isocyanate                                                                       Polyurethanes                                              Tetrabromophthalic acid or                                                                       Polyesters                                                 anhydride                                                                     Bromophthalimide   Nylon type polymers                                        Tetrabromobisphenol A                                                                            Epoxies                                                    Brominated salicylanilide                                                     ______________________________________                                    

A preferred class of halogen-containing organic compounds areDiels-Alder reaction products of brominated or chlorinatedcyclopentadiene with hydrocarbons, carboxylic acids or carboxylic acidanhydrides containing a carbocyclic ring structure and one or twocarbon-carbon double bonds. The carbocyclic compounds are represented bycyclopentadiene, maleic anhydride and 1-cyclohexene-3,4-dicarboxylicacid.

Suitable halogen-containing compounds do not volatilize to anysignificant extent at temperatures below 200° C.

The effectiveness of halogen-containing organic compounds as flameretardants is markedly increased by using the halogen-containing organiccompound in combination with antimony trioxide and a halogenatedphosphorus compound selected from tris(halophenyl) phosphates,tris(halophenyl) thiophosphates and bis(halophenyl) thiophosphorylchlorides, wherein each phenyl radical contains at least three halogenatoms selected from bromine and chlorine.

The weight of halogen-containing organic compound should be equal tobetween one and twelve times the weight of antimony oxide. A slightreduction in the minimum amount of halogen-containing organic compoundrequired can be achieved using a chlorinated paraffin wax as thehalogen-containing organic compound. The combination of antimony oxideand halogen-containing compound comprises between 20% and 40% by weightof the present flame retardant composition. Using a higher concentrationdoes not significantly improve flame retardancy and, more importantly,adversely affects the strength and other properties of the substratematerial.

The concentration of total flame retarding agent, i.e. the combinationof antimony oxide, halogen-containing organic compound, halogenatedphosphorus compound and, optionally, sulfur can be between 3% and 50% byweight of the substrate, depending upon the organic halogen source. As ageneral rule, a smaller amount of a bromine-containing compound will berequired than a chlorine-containing compound to obtain an equivalentlevel of flame retardant performance. The concentration ofhalogen-containing organic compound required to impart flame retardancyto the various classes of organic polymers is discussed in detail innumerous publications, and it is, therefore, not considered necessary torepeat these values in the present specification.

The flame retardants of this invention decrease the ability of amaterial to support flaming combustion following removal of the ignitingflame. They also have been shown to reduce or eliminate the "afterglow"which often persists once the flaming combustion has been extinguished.The glowing indicates that the material is continuing to smolder or burnslowly and may reignite into flaming combustion at a future time. Inaddition, the dripping of molten polymer from the heated material is forall intents and purposes eliminated. This cannot be achieved using priorart compositions, including those which employ substantially the samematerials as those of the present invention but in different proportionsthan those specified herein.

The flame retarding agents of this invention can be incorporated intothe inherently flammable polymer to be protected by combining the agentswith the polymer before the resultant composition is fabricated to forma final product, for example, by molding, casting, or extrusion.Alternatively, the agents can be incorporated into a suitable coatingmaterial which is applied as a film to the substrate by brushing,spraying, or dipping. The coating materials are usually prepared bydissolving or dispersing the flame retarding agent in a liquid vehicletogether with a suitable film-forming polymer. Suitable film-formingpolymers are well known in the art relating to coatings and will not bediscussed in the present specification. Poly(vinyl chloride) ispreferred for this use, since in addition to providing a film it alsofunctions as a source of available chlorine at flame temperatures. Theconcentration of flame retardant in the final film is between 20 and 40%by weight.

The Underwriter's Laboratory flammability test designated as UL 94provides a convenient means for evaluating the efficacy of flameretarding agents for plastic materials. The test is described in theFebruary, 1964 issue of the "Bulletin of Research for the Underwriter'sLaboratory, Inc.", pages 42 and 43. Test samples conforming to specifieddimensional limits are ignited, after which the igniting flame isremoved and the time required for both the flame and any subsequentglowing to extinguish themselves is measured. Those samples which arerated self-extinguishing are further classified in order of decreasingflammability as SE-II, SE-I or SE-O, depending upon the burning and/orglowing time and whether or not the molten drippings from the samplewill ignite cotton fibers placed below the sample. A rating of SE-IIindicates that only the solid polymer is self-extinguishing within anaverage time of 25 seconds, based on five trials, following removal ofthe igniting flame. The molten material which drips from the flamingsample may ignite untreated cotton fibers placed twelve inches (30 cm.)below the test sample. Samples which qualify as SE-I areself-extinguishing within an average time of 25 seconds followingremoval of the igniting flame and do not drip flaming molten material.Any localized glowing must cease within 30 seconds following removal ofthe flame, not travel for more than 0.5 inch and be incapable ofigniting surgical cotton. If the other SE-I requirements are met, theflame is extinguished within an average of five seconds followingignition, and no flaming particles are present, the samples are ratedSE-O. The appropriate Underwriter's Laboratory publications should beconsulted for a more complete description of the rating system employedfor the UL 94 test procedure.

The following examples demonstrate the efficacy of the flame retardingagents of this invention and should not be interpreted as limiting thescope of this invention. All parts are by weight unless otherwisespecified.

EXAMPLE 1

This example demonstrates the flame retardancy imparted to polypropyleneusing tris(2,4,6-tribromophenyl) phosphate in combination with antimonytrioxide and various halogen-containing organic compounds as the flameretarding agent.

Test samples were prepared by combining the indicated amounts of flameretardant with 100 parts by weight of a commercial grade of powderedpolypropylene manufactured by Hercules, Inc. (Profax® 6523) on atwo-roll mill. The resultant sheet was cut into pellets approximately0.125 inch (0.317 cm.) in diameter. The pellets were injection molded ata temperature between 218° and 234° C. to form bars measuring 6 inches ×0.5 inch × 0.125 inch (15 cm. × 1.3 cm. × 0.317 cm.).

The data obtained from the UL 94 test are disclosed in Tables I and II,Samples 1, 6, 8, and 10 in Table I did not contain any phosphate andwere employed as controls (CTRL). It should be noted that a class 0rating in accordance with the UL 94 test was only achieved using thehalogenated aromatic phosphate in combination with antimony oxide andthe halogen-containing organic compound.

                                      TABLE I                                     __________________________________________________________________________             1    2   3   4   5   6    7   8    9   10   11                       SAMPLE NO.                                                                             (CTRL)               (CTRL)   (CTRL)   (CTRL)                        __________________________________________________________________________    Polypropylene                                                                          100  100 100 100 100 100  100 100  100 100  100                      (ProfaxO .sup.R   6523)                                                       Antimony tri-                                                                 oxide    17   17  --  17  --  17   17  17   17  17   17                       DechloraneO .sup.R   .sup.(1)                                                          50   50  --  --  50  --   --  --   --  --   --                       ChloranO .sup.R   .sup.(2)                                                             --   --  --  --  --  --   --  50   50  --   --                       Dichlor 1O .sup.R  .sup.(3)                                                            --   --  --  --  --  50   50  --   --  --   --                       Octabromobi-                                                                  phenyl   --   --  --  --  --  --   --  --   --  50   50                       TTBPP .sup.(4)                                                                          0    5   5   5       0    5   0    5   0    5                       UL 94 Class                                                                            I     0  fails                                                                             fails                                                                             fails                                                                             I    I   fails                                                                               0  I     0                                         (7) (7) (7)          (7)                                    Average burning                                                               time .sup.(5)                                                                           7    2  --  --  --   5    5  --   <1   6    2                       Average after-                                                                glow time .sup.(6)                                                                     50    7  --  --  --  45   24  --    0  17    0                       __________________________________________________________________________    NOTES:                                                                        .sup.(1)                                                                         Perchloropentacyclodecane                                                  .sup.(2)            .sup.(3)                                                      ##STR5##                                                                                       ##STR6##                                                 .sup.(4)                                                                         tris-(2,4,6-tribromophenyl) phosphate                                      .sup.(5)                                                                         Elapsed time in seconds between ignition                                      of sample and extinguishing of flame                                          (6 trials).                                                                .sup.(6)                                                                         Elapsed time in seconds between extinguish-                                   ing of flame and disappearance of glowing,                                    as evidenced by red or orange-red colora-                                     tion (6 trials).                                                           .sup.(7)                                                                         Samples were too flammable to qualify in                                      any UL Class.                                                          

                  TABLE II                                                        ______________________________________                                        Profax® 6523 (parts)                                                                       200    200     200   200                                     Antimony Trioxide (parts)                                                                      40     40      40    34                                      Chlorinated Diels-Alder                                                                        40     80      80    100                                     Adduct.sup.1 (parts)                                                          TTBPP (See Table I) (parts)                                                                    40     40      20    20                                      Flame-out Time (seconds)                                                                       --      2       4    2                                       Afterglow Time (seconds)                                                                       --     20-60   20-60 6                                       UL 94 Rating     II     I       I     O                                       ______________________________________                                         Note:                                                                         .sup.1 A 2:1 mole ratio Diels-Alder reaction product of                       hexachlorocyclopentadiene and 1,5 -cyclooctadiene available under the         tradename "Dechlorane Plus".                                             

Control Samples 3, 4 and 5 demonstrate that tris(2,4,6-tribromophenyl)phosphate does not significantly reduce the flammability ofpolypropylene at the relatively low concentrations employed (5 parts)unless both the antimony oxide and halogen-containing organic compoundare present.

EXAMPLE 2

The procedures described in Example 1 were used to incorporatetris(2,4,6-tribromophenyl) phosphate into a commercially available flameretardant polypropylene composition which contains about 37% by weightof a 3:1 weight ratio mixture of perchloropentacyclodecane:antimonytrioxide. The addition of 10 parts by weight oftris(2,4,6-tribromophenyl) phosphate to 200 parts of the polypropylenecomposition resulted in a change in the UL 94 class from 1 to 0. Theburning time decreased from six seconds to substantially zero,indicating that the sample would not support flaming combustion in air.The afterglow time decreased from 40 seconds to two seconds followingaddition of the phosphate.

EXAMPLE 3

This example demonstrates the increase in efficiency of the flameretardant achieved by the incorporation of sulfur in combination with asuitable phosphorus compound. The test samples were prepared asdescribed in Example 1 and rated for flammability as described in the UL94 procedure. The composition and flame retardancy ratings aresummarized in Table III wherein all concentrations are expressed inparts by weight.

                  TABLE III                                                       ______________________________________                                                       Sample                                                                              Sample  Sample  Sample                                                  1     2       3       4                                        ______________________________________                                        Polypropylene (Profax®                                                     6523)           225     225     225   225                                    Perchloropentacyclo-                                                           decane          100     100     100   100                                    Antimony trioxide                                                                              33.4    33.4    33.4  33.4                                   Tris(2,4,6-tribromo-                                                           phenyl) phosphate                                                                             16.7    15.6    --    --                                     Bis(tribromophenyl)trichloro-                                                  phenyl phosphate                                                                              --      --      16.8  15.9                                   Sulfur           --      1.1     --    1.1                                    Flame-out time (seconds)                                                                       5.5     3.0     7.0   4.0                                    Afterglow time (seconds)                                                                       21.0    7.0     30.0  6.0                                    UL 94 Rating     SE-I    SE-O    SE-I  SE-O                                   ______________________________________                                    

EXAMPLE 4

This example demonstrates other phosphorus compounds suitable for use inthe flame retarding agents of this invention.

Using the procedure described in Example 1, test samples were preparedusing the following polymer composition:

Polypropylene (Profax® 6523); 100 parts

Antimony trioxide; 17 parts

Perchloropentacyclodecane; 50 parts

This composition was rated SE-I in the UL 94 vertical burning test. Theaddition of 8 parts of one of the following phosphorus compounds yieldeda test sample that was rated SE-O:

tris(2,4,6-tribromophenyl) phosphate

Tris(2,4,6-trichlorophenyl) phosphate

Bis(2,4,6-tribromophenyl)-2,4,6-trichlorophenyl phosphate

Bis(2,4,6-trichlorphenyl)-2,4,6-tribromophenyl phosphate

Tris(2,4,6-tribromophenyl)thiophosphate

Bis(2,4,6-tribromophenyl)thiophosphoryl chloride

Tris(pentabromophenyl)phosphate

EXAMPLE 5

Test samples were prepared and rated for flammability using theprocedures described in Example 1 and the polymer compositions set forthin Table IV. The concentration of the components comprising the flameretarding agents are expressed as parts by weight per 100 parts of thepolymer. As in the previous examples a UL 94 Test rating of "0" can beachieved only in the presence of the tris(2,4,6-tribromophenyl)phosphate.

                                      TABLE IV                                    __________________________________________________________________________                      Set 1 Set 2 Set 3 Set 4 Set 5 Set 6                         __________________________________________________________________________    Antimony trioxide (parts)                                                                       13 13 15 15 15 15 17 17 13 13 5  5                          Perchloropentacyclodecane (parts)                                                               25 25 30 30 30 30 50 50 25 25 -- --                         Tris(2,4,6-tribromophenyl)                                                    phosphate (parts) 0  8  0  8  0  8  0  8  0  8  0  8                          Acrylonitrile-butadiene-styrene                                               copolymer (1)(parts)                                                                            100                                                                              100                                                                              -- -- -- -- -- --                                     Polystyrene (parts)     100                                                                              100                                                                              -- -- -- --                                     Styrene-acrylonitrile                                                         copolymer (2) (parts)   -- -- 100                                                                              100                                                                              -- --                                     Polyethylene (parts)    -- -- -- -- 100                                                                              100                                    Poly(methyl methacrylate)(parts)                                                                      -- -- -- -- -- -- 100                                                                              100                              Hetron® 92 GT (3) (parts)                                                                         -- -- -- -- -- -- -- -- 100                                                                              100                        UL 94 Class       SE-I                                                                             SE-O                                                                             SE-I                                                                             SE-O                                                                             SE-I                                                                             SE-O                                                                             SE-I                                                                             SE-O                                                                             SE-I                                                                             SE-O                                                                             SE-I                                                                             SE-O                       __________________________________________________________________________     NOTES:                                                                        (1) Available as Blendex® 301 from Marbon Division of Borg-Warner         Corporation.                                                                  (2) Available as RMDA-4511 from Union Carbide Chemical Corporation.           (3) An unsaturated polyester derived from chlorendic anhydride, ethylene      glycol and diethylene glycol which has been crosslinked using styrene;        available from Hooker Chemical Corporation.                              

EXAMPLE 6

This example demonstrates that a flame retardant composition describedin British Pat. No. 1,076,608, which employs antimony oxide, abrominated aromatic phosphorus compound and a chlorine-containingparaffin in proportions which are outside the scope of this invention ismarkedly inferior in flame retarding ability when compared with thepresent compositions.

The following composition was prepared using the procedure described inExample 1:

Polypropylene 100 parts

Chlorinated Paraffin Wax (70% weight chlorine): 4 parts

Antimony Oxide: 5 parts

Tris(2,4,6-tribromophenyl)phosphate: 5 parts

The sample exhibited a rating of SE-II in the UL 94 test and producedflaming molten material when heated by the flame.

EXAMPLE 7

This example demonstrates the unique performance of halogenated aromaticphosphates as flame retardants for polypropylene. The degree of flameretardancy (UL 94 Class 0) cannot be achieved using an equalconcentration of phosphorus derived from representative inorganic ororganic phosphates other than those of the present invention. Theresults of the flammability tests are summarized in Table V.

                                      TABLE V                                     __________________________________________________________________________    Effect of Various Phosphorus Compounds on Flammability                        Component                                                                     __________________________________________________________________________    Polypropylene                                                                            200 200  200  200  200 200  200 200                                (parts)                                                                       Chlorinated Diels                                                                        100 100  100  100  100 100  100 100                                Alder Adduct.sup.1                                                            (parts)                                                                       Antimony Trioxide                                                                         34  34   34   34   34  34   34  34                                (parts)                                                                       TTBPP (parts)                                                                            --  16.7 --   --   --  --   --  --                                 Tris(dibromo                                                                  propyl)phosphate                                                                         --  --   12.0 16.7 --  --   --  --                                 (parts)                                                                       Ammonium Phosphate                                                                       --  --   --   --   2.2 16.7 --  --                                 (parts)                                                                       Tricresyl Phos-                                                               phate (parts)                                                                            --  --   --   --   --  --   5.8 16.7                               % Phosphorus                                                                  in Composition                                                                           0   .06  .06  .085 .06 .45  .06 .18                                UL94 Classifi-                                                                cation     I   O    I    I    I   F    I   I                                  Flameout time                                                                            5   5    5.5  9.5  3.5 --   9   9.5                                (sec.)                                                                        Afterglow time                                                                            29  10   35   23  --   32   31                                    (sec.)                                                                        __________________________________________________________________________     NOTE:                                                                         .sup.1 A 2:1 mole ratio Diels-Alder reaction product of                       hexachlorocyclopentadiene and 1.5 cyclooctadiene.                        

I claim:
 1. A flame retardant composition comprising (a) a polyolefin and (b) between 20 and 40%, based on the weight of said composition, of a mixture consisting of one part by weight of antimony oxide, between one and twelve parts of a halogen-containing organic compound exhibiting a volatilization temperature above 200° C. and selected from the group consisting of Diels-Alder adducts derived from two moles of a hexahalo-cyclopentadiene per mole of a cyclic hydrocarbon containing two carbon-carbon double bonds, perhalocyclopentadecanes and halogenated biphenyls, and 0.5 to about 15%, based on the combined weight of the antimony oxide and halogen-containing organic compound, of at least one phosphorus compound selected from the group consisting of tris (halophenyl) phosphates and tris (halophenyl) thiophosphates, wherein each phenyl radical exhibits at least three halogen atoms and all halogens present in said flame retardant composition are selected from the group consisting of bromine and chlorine.
 2. The flame retardant composition of claim 1 wherein the tris(halophenyl)phosphate is tris(2,4,6-tribromophenyl)phosphate.
 3. A flame retardant composition comprising (a) a polymer selected from the group consisting of polymers of acrylic acid esters, polystyrene, crosslinked products derived from unsaturated polyesters and copolymers of acrylonitrile with at least one comonomer selected from the group consisting of styrene and butadiene, (b) between 20 and 40%, based on the weight of said composition, of a mixture consisting of one part by weight of antimony oxide, between one and twelve parts of a halogen-containing organic compound exhibiting a volatilization temperature above 200° C. and selected from the group consisting of Diels-Alder adducts derived from two moles of a hexahalocyclopentadiene per mole of a cyclic hydrocarbon containing two carbon-carbon double bonds, perhalocyclopentadecanes and halogenated biphenyls, and between 0.5 and 20%, based on the combined weight of the antimony oxide and halogen-containing organic compound, of at least one tris(halophenyl)phosphate, wherein each phenyl radical exhibits at least three halogen atoms and all halogens present in said flame retardant compositions are selected from the group consisting of bromine and chlorine.
 4. The improved flame retardant composition of claim 3 wherein the tris(halophenyl)phosphate is tris(2,4,6-tribromophenyl)phosphate.
 5. A composition for enhancing the resistance of flammable polymers to both flaming and glowing combustion, consisting of one part by weight of antimony oxide, between one and twelve parts of a halogen-containing organic compound exhibiting a volatilization temperature above 200° C. and selected from the group consisting of Diels-Alder adducts derived from two moles of a hexahalocyclopentadiene per mole of a cyclic hydrocarbon containing two carbon-carbon double bonds, perhalocyclopentadecanes and halogenated biphenyls, and 0.5 to about 20%, based on the combined weight of the antimony oxide and halogen-containing organic compound, of at least one phosphorus compound selected from the group consisting of tris(halophenyl)phosphates and tris(halophenyl)thiophosphates, wherein each phenyl radical exhibits at least three halogen atoms and all halogens present in the flame retardant are selected from the group consisting of bromine and chlorine.
 6. The composition of claim 5 wherein the tris(halophenyl)phosphate is tris(2,4,6-tribromophenyl)phosphate. 